Instrument for elbow surface replacement arthroplasty

ABSTRACT

A bone cutting device for precision elbow surface replacement arthroplasty and osteotomy is described. A humeral clamping device is provided with an outrigger to hold the ulna in preselected and rigid relation to the humerus. A bond cutting tool such as a burr is inserted into a selected guide sleeve mounted for oscillatory arcuate movement on the medial side of the clamping device, so as to precisely prepare the humerus. The humeral guide sleeve is removed and replaced with a slightly longer second sleeve which provides the precise spacing required to prepare the ulna in similar manner. A planar radial cutting guide may be mounted on the lateral side of the clamping device, to guide a planar oscillating saw used to prepare the proximal end of the radius.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.730,931 filed May 6, 1985, now U.S. Pat. No. 4,624,250 which in turn isa continuation-in-part of our earlier filed U.S. patent application Ser.No. 507,378 filed June 24, 1983, now abandoned, the disclosure of whichis incorporated herein by reference.

FIELD OF INVENTION

This invention relates to an orthopaedic joint clamping and bone cuttingdevice. More particularly this invention relates to a bone cuttingdevice for precision elbow surface replacement arthroplasty andosteotomy.

BACKGROUND OF INVENTION

The complex kinematics, anatomical features and load distribution on anelbow are such that surgical replacement thereof is not simple. Simpleconstrained and semi-constrained cemented replacements for the elbowjoint have proved to be generally unsatisfactory as they do not providesufficient range of motion and, due to the unnatural stresses placed onthe musculature, ligaments and tendons, premature loosening often withina year or two of placement frequently occurs. Loosening is usuallyaccompanied by pain and discomfort and over a period of time distortionof the natural function of the joint may occur. The use of unconstrainedresurfacing prostheses, such as those described in the aforesaidapplication Ser. No. 507,378 and in U.S. Pat. No. 4,242,758 issued Jan.6, 1981 to Amis et al, appears to offer the potential, by reproductionof normal joint geometry and restoration of ligament balance, torecreate relatively normal kinematics and load bearing and to providerelief of pain. Such prostheses are now generally using the relativelyrecently developed porous metal coating technique so as to promote boneingrowth, and this technique precludes the use of cements to secure theprosthesis to the bone or to compensate for cutting inaccuracies. It isnow necessary to ensure accurate resection of the bone ends to within atolerance of 1 mm or better. Such accuracies are not possible usingcommonly available jigs or with hand held saws or other cutting toolssuch as router tools.

OBJECT OF INVENTION

It is therefore an object of the present invention to provide a novelsurgical method to hold an elbow joint in a preselected position so asto accurately resect the humeral, ulna and radial bones without movingthe joint between cuts. The cuts are precisely positioned to receive aresurfacing prosthesis, of one of five preselected standard sizes, suchas that described in our application for U.S. Letters Patent entitled"Elbow Prosthesis" Ser. No. 730,814 filed May 6, 1985.

BRIEF STATEMENT OF INVENTION

By one aspect of the invention there is provided a method for surgicallyimplanting an elbow prosthesis comprising:

(a) exposing medial and lateral epicondyles of an elbow to be replaced;

(b) removing a crown from each of said medial and lateral epicondyles soas to provide flattened epicondylar plateaus;

(c) determining a geometric trochleal centre and a geometric capitellumcentre on respective ones of said epicondylar plateaus, and drillingpilot holes thereat;

(d) mounting a width-adjustable humeral clamp, provided with a pair ofmounting pins, on said elbow by inserting said pins into respective onesof said pilot holes, adjusting the width of said clamp and securing in aselected orientation by insertion of at least one lateral locking pin;

(e) mounting one end of a longitudinally extending ulna fixationassembly on said humeral clamp perpendicularly thereto; said ulnafixation assembly having an adjustable crosshead assembly at the freeend thereof, coronoid arms extending from each end of said crossheadassembly and an olecranon bracket extending intermediate the ends ofsaid crosshead and angularly adjustable so that a pin extending throughthe free end thereof into the olecranon is substantially parallel to theaxis of said ulna;

(f) securing said ulna and humerus at an inclined angle of about 135degrees with strap means between the distal end of the ulna and theproximal end of the humerus;

(g) securing said pin extending through the olecranon bracket in a planeparallel the axis of said ulna;

(h) mounting a selected humeral cutting cam on said humeral clamp on themedial side thereof;

(i) inserting a cutting means through said cutting cam and shaping thetrochleal and capitelum portions of the distal end of said humerustherewith;

(j) replacing said humeral cutting cam and cutting means with a selectedulna cutting arc template;

(k) inserting said cutting means through said cutting arc template andshaping the proximal end of said ulna therewith;

(l) mounting a radial cutting gauge on the lateral side of the humeralclamp and resecting the proximal end of the radius;

(m) removing said humeral clamp from said elbow;

(n) mounting a radius prosthesis on said resected radius from thelateral side of the elbow;

(o) slidingly inserting a humeral prosthesis on said humerus from themedial side;

(p) slidingly inserting an ulna prosthesis on said prepared ulna fromthe medial side;

(q) replacing said medial and lateral epicondyles; and

(r) closing both medial and lateral wound sites.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of a trochlear template;

FIG. 2 is a plan view of a capitellum template;

FIG. 3 is a front view of a humeral clamp according to the invention;

FIG. 4 is a side view of a humeral clamp of FIG. 3 with an ulnaoutrigger installed;

FIG. 5 is a bottom view of the device of FIG. 4

FIG. 6 is a diagramatic sketch of the device of FIG. 4, in position onan elbow;

FIG. 7 is a side view of a humeral cutting cam;

FIG. 8 is a plan view of a radius gauge;

FIG. 9 is a side view of a radius centre pin cutter;

FIG. 10 is a side view of a radial prosthesis;

FIG. 11 is a plan view of the prosthesis of FIG. 10;

FIG. 12 is a front view of a humeral prosthesis

FIG. 13 is a sketch of an anterior view of a right elbow including thehumeral, ulnar and radial prosthesis of the present invention;

FIG. 14 is a medial view of an ulna prosthesis; and

FIG. 15 is an anterior view of the prosthesis of FIG. 14.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the copending application Ser. No. 730,814 filed May 6, 1985, a novelhumeral resurfacing prosthesis which substantially replicates the distalend of a humerus is described. While it was first thought that the useof external anatomical landmarks, such as the epicondyles, would providethe means to establish the radial centre for the convex semi-circularcut at the distal humerus necessary to receive the prosthesis, thisapproach was discarded as it was found that the axis (or C-line) of thetrochlea and capitellum, which is substantially a straight line, is infact at an angle of about 2°-3° to the transepicondylar line (TEL).Instead use is made of the curved surface of the trochlea andcapitellum. An incision is made first on the medial side of the elbowand, after drilling a pilot hole in the centre of the medial epicondyle,the epicondylar crown is removed (for later replacement and securementby a screw inserted into the pilot hole). A series of differently sizedsemicircular trochlear templates 10 are placed on the now flattenedmedial epicondylar plateau to establish, by a "best fit" approach, thegeometric centre of the medial aspect of the trochlear, which is thenmarked and a pilot hole drilled thereat. After making an incision andexposing the lateral side the procedure is repeated with a series ofcapitellum templates 101, which establishes the geometric centre of thecapitellum.

A U-shaped width-adjustable humeral clamp 12 with locating pins 13,14 atthe ends of the areas thereof, is placed on the humerus and the pinslocated in the respective trochlea (medial) and capitellum (lateral)pilot holes. Once the pins are located, the arms 15,16 of the clamp areadjusted towards each other by sliding integral sleeves 151,152 alongrespective guide rods 153,154 and locked in place by clamping screw 17thereby securely locating the clamp and yet still allowing it to berotated about the C-line axis of the humerus. A humeral cutting cam 18(FIG. 7) of selected length is axially mounted on shouldered guide pin42 at the end of the medial arm 15 of the clamp and rotatably secured bymeans of locking nut 19 as seen in FIG. 3. The cam 18 comprises a body20, having a circular hole 21 therethrough adjacent one end, adapted tobe mounted on pine 42 which is in turn arranged to receive locking screw19, and about which body 20 may be arcuately oscillated, and a hollowguide 22 axially parallel to and spaced a selected distance from hole21. Guide 22 is adapted to receive a rotatable burr (not shown)generally about 1/8" in diameter. The burr may be rotated by anyconventional power or air tool normally found in an operating theatre.The cam with the burr in place is oscillated back and forth to ensurethat the correct cutting arc has been established. Once the surgeon issatisfied with the cutting arc, cam 18 may be removed if desired. A3/32" Steinman pin 24 is then inserted through hole 23 in the clamp 12and screwed into the underlying prepared surface of the medialepicondyle. This prevents the clamp from rotating on its axis. A similarSteinman pin may be inserted through complementary pilot hole 25 on thelateral side to further assist in rigidly mounting the clamp. The ulnafixation assembly 26 is next mounted on the humeral clamp by means ofU-clamp 27. The ulna fixation assembly 26 comprises a telescopicallyexpandable arm 28, lockable at any selected length by U-clamp 29. Acrosshead 30 is adjustably and clampingly mounted at the end of arm 28by means of clamp 31 intermediate the ends thereof. Coronoid arms 32, 33extend substantially perpendicularly to arm 28 and to crosshead 30 atopposite ends thereof and angularly adjustable relative thereto.Intermediate the ends of crosslead 30 there is provided an olecranonbracket 34 which may be locked at any desired angle to arms 32, 33 bymeans of locking screws 35, 36. The olecranon bracket 34 is adjusted sothat the adjustable pin clamp 37 lies adjacent the olecranon, and athreaded Steinman pin 38 may be inserted through clamp 37 and drillednot more than about 1 cm into the olecranon so that pin 38 issubstantially parallel to the longitudinal axis of the ulna. With theelbow flexed at about 45°, and held at that angle by a rigid,telescopically adjustable bracket 83 and wrist 81 and humeral straps thelinked, parallel coronoid bracket arms 32, 33 are adjusted to lieadjacent the coronoid areas on their respective side of the ulna. A5/32" threaded Steinman pin may now be inserted through medial guidehole 39, drilled through the ulna and into the guide hole 40 on thelateral side. When all the pins are in place and the surgeon issatisfied with the orientation of the ulna and radius relative to thehumerus, the adjustment 26,27,31,35,36,37,41, are locked in place tohold the ulna and humerus in the selected orientation.

A selected humeral cutting cam 18 is then remounted, if previouslyremoved, on pin 42 and secured by nut 19, preparatory to making thehumeral cuts. A selected rotatable burr, preferably provided with adepth control gauge (not shown) inserted into hole 22 and may then beactuated by any conventional air or electric power source. Onceinserted, it is preferable to drill to full depth at each extreme ofarc. Subsequently, the cam may be moved in either direction, butgenerally counterclockwise, to remove the remainder of the bone in thetrochleal cutting arc, cutting to a depth of about 1 cm at a time andspraying the burr continuously with a sterile saline solution to preventoverheating of the bone and to wash away debris. Once the trochlealsurface has been removed, and it is here emphasized that the presentprotocol is designed to remove a minimum of bone stock, the depthcontrol gauge is adjusted to the depth required to cut the capitellumportion, and the capitellum is cut in similar manner to the trochlea.Without removing the clamp from the humerus and ulna, the humeralcutting cam is removed and replaced with an ulna cutting cam which issimilar in shape to humeral cutting cam 18, but with a slightly larger,and predetermined selected cutting radius. It will be appreciated that,according to our copending application "Elbow Prosthesis" filed May 6,1985, Ser. No. 730,814, it has been possible to generate 5 standardsizes of humeral prostheses to fit 95%, of the population. Complementaryulna and radial prostheses of varying thickness are also available, sothat the surgeon may select the most suitably sized humeral prosthesisand match it with a similarly standardized ulna or radial prosthesis.Thus the clearance required between the humeral and ulna prepared bonesurfaces is readily predetermined, and the exact cutting radius for theulna cutting cam selected. Once selected, positioned and locked in placeby nut 19, the depth gauge is set and cutting of the ulna proceeds in asimilar manner to the humeral cut, it being perferred to rotate the ulnacam in a clockwise manner.

The ulna cam is then removed and a flat radius cutting gauge (not shown)is locked in appropriate orientation on the humeral clamp on the lateralside 16 thereof. Using the flat surface thereof as a guide for anorthopaedic oscillating saw (not shown) the head of the radius isresected.

Any excess bone or cartilage tissue, which might interfere withprosthesis implantation may be trimmed away, from the medial side, bymeans of selected profile tools and osteotones. Generally such tools maybe guided by means of guides (not shown) mounted on the humeral frame.The frame can then be dismounted from the ulna and humerus.

The arm may then be rotated to the lateral side and a radius gauge 51(FIG. 8) is selected, from a sized set thereof, which most closelycorresponds in diameter to that of the radius and placed over thesquarely prepared proximal end of the radius. A marker probe is insertedthrough hole 52 and used to mark the centre of the radius. The gauge 51is then removed and replaced by radius centre pin cutter 53 (FIG. 9) thecentering pin 54 of which is inserted into the marked centre of theradius. The cutter 55 is tapped home by means of a small osteotone whichis struck against strike 56. The cutter 53 is then rotated axially aboutpin 54, in an arc of about 45° in each direction and then removed, thusremoving a cylindrical core of bone from the radius. The radialprosthesis 88 (FIGS. 10, 11) is then inserted with the stem 81projecting into the cored hole formed in the radius. The prosthesis istapped into position by placing the convexly contoured surface 57 totool 53 over the concave surface 89 of prosthesis 88 and strikingstriker 58 with a small osteotone.

The arm is again rotated to the medial side and the humeral prosthesis92 (FIG. 12) is inserted into position, as shown in FIG. 13, tapping ifrequired to achieve the desired position and taking care not to disturbthe radial prosthesis. The ulna prosthesis 63 (FIGS. 14, 15) is theninserted, also from the medial side, and its position adjusted asnecessary. Locating pins, if used, are pressed into the underlying ulnabone. Using a bone screw inserted into the predrilled pilot hole, themedial epicondyle is replaced, oriented and secured in place, and afterchecking to ensure alignment and free movement, the medial and lateralwounds may be closed.

We claim:
 1. A method for surgically implanting an elbow prosthesiscomprising:(a) exposing medial and lateral epicondyles of an elbow to bereplaced; (b) removing a crown from each of said medial and lateralepicondyles so as to provide flattened epicondylar plateaus; (c)determining a geometric trochleal centre and a geometric capitellumcentre on respective ones of said epicondylar plateaus, and drillingpilot holes thereat; (d) mounting a width-adjustable humeral clamp,provided with a pair of mounting pins, on said elbow by inserting saidpins into respective ones of said pilot holes, adjusting the width ofsaid clamp and securing in a selected orientation by insertion of atleast one lateral locking pin; (e) mounting one end of a longitudinallyextending ulna fixation assembly on said humeral clamp perpendicularlythereto; said ulna fixation assembly having an adjustable crossheadassembly at the free end thereof, coronoid arms extending from each endof said crosshead assembly and an olecranon bracket extendingintermediate the ends of said crosshead and angularly adjustable so thata pin extending through the free end thereof into the olecranon issubstantially parallel to the axis of said ulna; (f) securing said ulnaand humerus at an inclined angle of about 135 degrees with strap meansbetween the distal end of the ulna and the proximal end of the humerus;(g) securing said pin extending through the olecranon bracket in a planeparallel the axis of said ulna; (h) mounting a selected humeral cuttingcam on said humeral clamp on the medial side thereof; (i) inserting acutting means through said cutting cam and shaping the trochleal andcapitelum portions of the distal end of said humerus therewith; (j)replacing said humeral cutting cam and cutting means with a selectedulna cutting arc template; (k) inserting said cutting means through saidcutting arc template and shaping the proximal end of said ulnatherewith; (l) mounting a radial cutting gauge on the lateral side ofthe humeral clamp and resecting the proximal end of the radius; (m)removing said humeral clamp from said elbow; (n) mounting a radiusprosthesis on said resected radius from the lateral side of the elbow;(o) slidingly inserting a humeral prosthesis on said prepared humerusfrom the medial side; (p) slidingly inserting an ulna prosthesis on saidprepared ulna from the medial side; (q) replacing said medial andlateral epicondyles; and (r) closing both medial and lateral woundsites.
 2. A method as claimed in claim 1 wherein said geometrictrochleal and capitellum centres are determined by means of templates ofselected size.
 3. A method as claimed in claim 1 wherein said proximalend of said ulna and said distal end of said humerus are shaped using arotatable burr inserted through said cutting cam.
 4. A method as claimedin claim 2 wherein said radius is resected with an oscillating cuttingmeans guided by said cutting gauge.